In recent years, it has been known a cartridge-type electrophotographic image forming apparatus with a low running cost and easy maintenance. In the image forming apparatus, exchange of consumables such as the electrophotographic photosensitive member and the developer (hereinafter referred to as toner) is enabled to reduce the running cost. Such a technique for satisfying that the exchange of the consumables such as the photosensitive member or the toner is enabled to reduce the running cost has been described (Japanese Patent No. 3592522). In this technique, in a state in which a photosensitive member unit (image bearing member unit) including a photosensitive drum and a developing unit accommodating the toner are mounted in a holder member, the holder member can be pulled out from a main assembly of an electrophotographic image forming apparatus.
In the electrophotographic image forming apparatus described in Japanese Patent No. 3592522, when the image bearing member unit is demounted from a pull-out member, a positioning supporting shaft is required to be demounted. Further, when a developing device is demounted from the pull-out member, a knob is required to be demounted from a central shaft of the developing device. Here, the positioning supporting member is inserted into a hole provided in a front side plate of the pull-out member, a hole provided in a side plate of the unit holder, and a center hole formed in a flange member on the front side of the image bearing member. Further, the knob is rotatably supported by the front side plate of the pull-out member through a bearing and is detachably mounted on a central shaft end portion on the more front side than the front side plate. Therefore, when the image bearing member unit and the developing device are demounted from the pull-out member, the above-described positioning supporting shaft and knob are required to be demounted. As a result, it is considered that it takes much time.